1. Field of the Invention
The present invention relates to a piezoelectric vibrator, and particularly to a piezoelectric vibrator which uses in a vibrating gyroscope for detecting a rotational angular velocity.
2. Description of the Prior Art
FIG. 6 is a perspective view showing an example of a vibrating gyroscope using a conventional piezoelectric vibrator, and FIG. 7 is its sectional view. A vibrating gyroscope 1 includes a piezoelectric vibrator 2. The piezoelectric vibrator 2 includes a vibrating body 3 having, for example, a regular triangular prism shape. Piezoelectric elements 4a, 4b and 4c are formed respectively on three side faces of the vibrating body 3. A ridge line of the vibrating body 3 between the piezoelectric elements 4a and 4b is supported by supporting members 5 at the portions in the vicinity of two nodal points . An oscillation circuit is connected between the piezoelectric elements 4a, 4b and the piezoelectric element 4c. The piezoelectric elements 4a and 4b are connected to a differential circuit. The differential circuit is connected to a detection circuit, and the detection circuit is connected to a smoothing circuit.
The vibrating body 3 makes a bending vibration in a direction perpendicular to the face of the piezoelectric element 4c by a signal of the oscillation circuit. When a rotational angular velocity is not applied to the vibrating gyroscope 1, the piezoelectric elements 4a and 4b bend in the same state, and the same signals are supplied to the differential circuit. Thus, the signals are offset in the differential circuit, and an output signal is not obtained from the differential circuit. When the vibrating gyroscope 1 rotates about an axis of the vibrating body 3, the direction of bending vibration of the vibrating body 3 changes by Coriolis force. Thus the bending states of the piezoelectric elements 4a and 4b change, and different signals are obtained from the piezoelectric elements 4a and 4b connected to the differential circuit. Then, an output signal is obtained from the differential circuit, and the output signal is detected by the detection circuit, and smoothed by the smoothing circuit. Since the smoothed signal corresponds to a rotational angular velocity, the rotational angular velocity applied to the vibrating gyroscope 1 is detected by measuring the smoothed signal.
However, in the vibrating gyroscope, though the supporting members are attached to the ridge line of the vibrating body at portions in the vicinity of nodal points, a vibration leakage from the supporting members can not be prevented because the real nodal points exist on a central axis of the vibrating body. By the reason, in the vibrating gyroscope using such piezoelectric vibrator, stable drift characteristics can not be obtained.